Drag and drop operations in a graphical user interface

Abstract: A technique for transferring a graphical object in a graphical user interface on a computer display from a source window to a target window. It is determined that a graphical object from the source window has entered the target window during a drag and drop operation. Next, it is determined that the graphical object has hit an interior boundary of the target window. The target window is scrolled so long as the graphical object continues to hit the interior boundary. Once the target location is visible in the target window, the graphical object is located at the target location at conclusion of the drag and drop operation. Some target windows of the graphical user interface are scrollable during a drag and drop operation with a graphical object from a foreign window, while some windows are not. Thus, in a mixed graphical user interface, it must be determined whether the target window is scrollable during a drag and drop operation.

Description: This invention relates generally to a graphical user interface of a data processing system. More particularly, the invention relates to a drag and drop operations in a graphical user interface. It is well known to provide a Graphical User Interface (GUI) to allow a user to control a computer system. A graphical user interface is used to present items which may be selected by the user and the results of such selection on the display. In a graphical user interface applications and data files are generally represented by a plurality of graphical objects such as windows or icons. It is known to allow a user to move graphical objects within a window or between windows through a "drag and drop" operation. During a drag and drop operation, the user selects an item such as a data file, represented by a graphical object such as an icon by moving the mouse pointer to the graphical object in the interface. Then, one or more buttons on the mouse are depressed and held while the user moves the mouse pointer through the GUI to the desired change of position. The desired change of position may simply be for a more aesthetically pleasing arrangement of the interface, or, in the case of a transfer between windows, may represent a transfer of data between applications or data files. The user then releases the button or buttons and the graphical object is "dropped" and placed at the new position in the interface. Logical changes are also made as a result of this operation such as storing the new position in the data structures which support the GUI as well as placing the data file represented by the icon into a new file structure, represented by the window to which the icon was moved. A drag and drop technique of this general type is described in EP-A-514307. Where the drag and drop operation involves a transfer from window to window and the space allocated for each window is not sufficient to display the entire window user interface, the drag and drop operation is somewhat cumbersome, particularly when the desired location in the target window is not displayed. The user can use the scroll bar in the target window to move the desired position into the target window's display space. Then, the object to be moved is dragged and dropped from the source location onto the target position. Alternatively, if the target position is not visible in the target window, the icon may be dropped at an arbitrary position in the target window. Then the user may use the scroll bar and drag and drop techniques together to move the icon to the target position. An article entitled 'Visual Semiotics of a Drag/Drop, Scrolling List', IBM Technical Disclosure Bulletin vol 36, no 06A, June 1983, pages 109-110 describes a technique for dragging and dropping items in a list. If required the list will scroll during a drag action. There is no discussion of transferring graphical objects from a target window to a source window. It is an aim of the present invention to solve or ameliorate the disadvantages of prior techniques. Accordingly there is provided a method for transferring graphical objects from a source window to a target window of a graphical user interface on a computer display, the method being characterised by the steps of: during a first drag a drop operation in a first mode, determining that a first graphical object has hit an interior boundary of the target window, scrolling the target window so long as the first graphical object continues to hit the interior boundary and locating the first graphical object at the target location at a conclusion of the first drag and drop operation; and during a second drag and drop operation in a second mode, which prevents the scrolling of the target window, dragging a second graphical object from the source window past an interior boundary of the target window. A system for carrying out the claimed method is also provided. A preferred method and system operate in a mixed graphical user interface wherein some target windows are scrollable during a drag and drop operation with a graphical object from a foreign window, while some windows are not. Thus, in a preferred system and method a determination is made as to whether the target window is scrollable during a drag and drop operation. A scrollable window can be determined to be scrollable either by referring to a class of the target window or by referring to a list of scrollable target windows. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 illustrates a computer comprising, system unit, keyboard, a mouse and a display; FIG. 2 is an architectural block diagram of a computer illustrated in FIG. 1; FIG. 3 shows a graphical user interface in which a drag-drop operation according to the principles of the present invention is performed; FIGS. 4A-4D are a flow chart depicting the drag and drop operation according to the preferred embodiments of the present invention; FIG. 5 is a data structure which can be used for identifying the windows which can be selectively scrolled. The invention may be run on a collection of computers under a number of different operating systems. The computers in the network could be, for example, a personal computer, a mini computer, mainframe computer or a computer running in a distributed network of other computers. Although the specific choice of computer is limited only by disk and disk storage requirements, computers in the IBM PS/2 (TM) series of computers could be used in the present invention. For additional information on IBM's PS/2 series of computers, the reader is referred to Technical Reference Manual Personal Systems/2 Model 50, 60 systems IBM Corporation, Part No. 68X2224 Order Number S68X-2224 and Technical Reference Manual Personal Systems/2 (Model 80) IBM Corporation Part No. 68X 2256 Order Number S68X-2254. One operating system which an IBM PS/2 personal computer may run is IBM's OS/2 2.0 (TM). For more information on the IBM OS/2 2.0 Operating System, the reader is referred to OS/2 2.0 Technical Library, Programming Guide Vol. 1, 2, 3 Version 2.00 Order Nos. 10G6261, 10G6495, 10G6494. In the alternative, the computer system might be in the IBM RISC System/6000 (TM) line of computers which run on the AIX (TM) operating system. The various models of the RISC System/6000 are described in many publications of the IBM Corporation, for example, RISC System/6000, 7073 and 7016 POWERstation and POWERserver Hardware Technical reference, Order No. SA23-2644-00. The AIX operating system is described in General Concepts and Procedure--AIX Version 3 for RISC System/6000 Order No. SC23-2202-00 as well as other publications of the IBM Corporation. In FIG. 1, a computer 10, comprising a system unit 11, a keyboard 12, a mouse 13 and a display 14 are depicted. The screen 16 of display device 14 is used to present the graphical user interface (GUI). The graphical user interface supported by the operating system allows the user to use a point and shoot method of input, i.e., by moving the mouse pointer 15 to an icon representing a data object at a particular location on the screen 16 and pressing one of the mouse buttons to perform a user command or selection. FIG. 2 shows a block diagram of the components of the personal computer shown in FIG. 1. The system unit 11 includes a system bus or plurality of system buses 21 to which various components are coupled and by which communication between the various components is accomplished. The microprocessor 22 is connected to the system bus 21 and is supported by read only memory (ROM) 23 and random access memory (RAM) 24 also connected to system bus 21. A microprocessor in the IBM multimedia PS/2 series of computers is one of the Intel family of microprocessors including the 386 or 486 microprocessors. However, other microprocessors included, but not limited to, Motorola's family of microprocessors such as the 68000, 68020 or the 68030 microprocessors and various Reduced Instruction Set Computer (RISC) microprocessors manufactured by IBM, Hewlett Packard, Sun, Intel, Motorola and others may be used in the specific computer. The ROM 23 contains among other code the Basic Input-Output system (BIOS) which controls basic hardware operations such as the interaction with the disk drives and the keyboard. The RAM 24 is the main memory into which the operating system and application programs are loaded. The memory management chip 25 is connected to the system bus 21 and controls direct memory access operations including, passing data between the RAM 24 and hard disk drive 26 and floppy disk drive 27. The CD ROM 32, also coupled to the system bus 21, is used to store a large amount of data, e.g., a multimedia program or large database. Also connected to this system bus 21 are various I/O controllers: the keyboard controller 28, the mouse controller 29, the video controller 30, and the audio controller 31. As might be expected, the keyboard controller 28 provides the hardware interface for the keyboard 12, the mouse controller 29 provides the hardware interface for mouse 13, the video controller 30 is the hardware interface for the display 14, and the audio controller 31 is the hardware interface for the speakers 15a and 15b. The speakers 15a and 15b may be used to present audio objects to the user. An I/O controller 40 such as a Token Ring Adapter enables communication over a network 46 to other similarly configured data processing systems. A preferred method of the present invention is implemented by means of a set of instructions in a code module resident in the random access memory 24. Until required by the computer system, the set of instructions may be stored in another computer memory, for example, in the hard disk drive 26, in an optical disk for eventual use in the CD ROM 32 or in a floppy disk for eventual use in the floppy disk drive 27. As shown in the figure, the operating system 50 and presentation manager 52 are resident in RAM 24. In this example, the instructions are embodied as an adjunct module onto the operating system. Alternatively, the graphical user interface could be incorporated into a standalone application 54, e.g., a monitor program 54 which monitors a database 56. FIGs. 3A, 3B and 3C, illustrate a source window 100 and a target window 101. The invention finds particular application in a database where each column of data is represented by an icon. By dragging the icon from source 100 to target window 101 which graphically represent two database tables within the database that column of data from the source window is added to the database table represented by the target window 101. In this example, target window 101 has been designated as providing scrolling capability during the drag-drop operation according to the principles of the invention. The target window may be so designated by a classification of window type in the GUI or by use of the list structure depicted in FIG. 5. Other windows in the GUI may not support scrolling during drag-drop operations if not deemed appropriate by the developer. As can be seen in FIG. 3A, the user drags the icon 103 from the source window 100 to the target window 101. As depicted in FIG. 3B, the icon 103 hits the boundary 105 of the target window 101 which causes scrolling until the user finds the target position 107 in the target window as shown in FIG. 3C. The user then drops the icon 103 on this position 107 to complete the operation. The GUI may include an indicia 109 such as an icon which can indicate to the user that the window behaves in this manner. Typically, a mouse is used to perform the drag and drop operation, but those skilled in the art will recognize that other pointing devices such a trackball or stylus can be employed. FIGs. 4A-4D depict the process of the preferred embodiment. The process begins in step 150 and proceeds to step 151, where a mouse button down event on an icon, in this case a column icon, is detected. In step 153, the variable Source Column is set to the selected column indicated by the mouse button down event and the variable CPos is set to the current mouse position. Next, the system loops in step 155 until the next user input such as a keyboard or mouse event occurs. If the event is a mouse drag event, as detected by step 157, the drag operation variables are set in step 159. The Drag Drop variable is set to "on" and the Entered variable is set to "off". The selected column icon is duplicated and displayed at the current mouse position, the variable PPos is set to the mouse position when the drag-drop operation began and CPos is allowed to vary according to the current mouse position. The process continues to FIG. 4B at this point unless a mouse button up event is detected in which case the process proceeds to the flow depicted in FIG. 4C. If other types of operations are detected in step 163 such as keyboard input the normal default processing is performed by the operating system in step 165. The process returns, step 166. If a mouse button down event at a column icon was detected again indicating selection of a different icon, in step 167, the process returns to step 153. The drag operation is continued in Fig. 4B where the mouse enters a target window and the mouse pointer hits an inside window boundary. The fact that the mouse is entering a window is determined by the saved position of the mouse position when the drag-drop operation began in the source window and its current position in the target window. The fact that the mouse pointer has hit the window boundary is determined by the coordinates of the current position of the mouse pointer and those of the window boundary. If the test in step 169 determines that the mouse is entering a target window which supports scrolling during drag-drop, such as the primary key definition window, in step 179, the Entered variable is set to "on". In step 181, a test is performed to determine whether the window is scrollable. The fact that the window is scrollable may be defined by the operating system or by the application developer at the creation of the window. If the window is scrollable, in step 183, the Scroll Move variable is set to "on". At the conclusion of either step 177 or step 183 and where a negative determination is made in step 181, the process returns to the loop at step 155 waiting for the next input event. As the user continues the drag operation the process will return to step 169, the test performed to determine whether the mouse is entering a target window which exhibits the invention's behavior the primary key definition window will be negative. Therefore, in step 171, a test is performed to determine whether the Entered variable is set to "on". If so, a test in step 173, determines whether the mouse pointer has hit the target window boundary. If the mouse pointer has hit the primary key definition window boundary, in step 175 a test is performed to determine whether the window is scrollable, e.g., if the Scroll_Move variable is "on". If so, the flow continues to FIG. 4D. If the process fails any of these tests, in step 177, the default behavior defined by the operating system is carried out. Referring to FIG. 4C, if a mouse button up operation is detected (Step 161, FIG. 4A), in step 191, a test is performed to determine whether the Entered and Drag-Drop variables are set to "on". If they are, it means that the user has dragged an icon into a moveable target window and is now ready to drop that icon on the target position. In step 193, a new object is created in the target window such as a new column of data in a database table, based on the information from the selected icon from the source window. The new column's position in the target window is determined based on the dropping location. In step 195, the source object column is marked to indicate that it has been selected. In step 197, the Entered, Drag-Drop, and Scroll move variables are set to "off". The process returns, step 199. In FIG. 4D, in response to a drag operation in which the tests in steps 171, 173 and 175 have succeeded, the test in step 201 determines whether the keystroke for non-scrolling is on. Step 201 provides an escape mechanism so that the mouse pointer can be dragged out of a target window or an intermediate window located between the source and target windows which also behaves according to the principles of the present invention. If the keystroke for non-scrolling is on, normal operations as defined by the operating system are, performed in step 177. Assuming, however, that the keystroke for non-scrolling is not on, the target window is scrolled according to the boundary value. In step 205, the CPos variable is set to equal PPos, which was the position at the scrolling the drag-drop operation started. One important key to note in the flow charts above, is setting the mouse position. Usually, the mouse position is known by querying the window management system. However, the previous mouse position must be stored to restrain the real mouse position. When the mouse pointer hits the boundary of a target window, even though the user is dragging the mouse away from the window, the dragging operation will not trigger the redisplay of the mouse icon with the dragging operation while the window is scrolling. Since the mouse position is reset each time, if the mouse is being detected as hitting the window boundary as long as the mouse button is still down, it will be determined as a drag operation, even though there is no mouse movement. The user still has the freedom to move the mouse out of the target window by pressing a predefined key, e.g., the control key, while dragging. The invention can be applied not only to windows of a certain class such as a primary key definition window in the example above, but also those windows which have been selected to have the behavior of the present invention. As long as the window is scrollable, a user may be specify that the method described in this invention should be used when an icon is dragged into it, i.e., scrolling while dragging. The data structure depicted in FIG. 5, is a simple list of window ids with pointers for the next window id in the list. This data structure can be used by the operating system to identify whether the behavior of this invention should be provided. The window id is generally used as a key to access any of the information about a window in most operating systems or window management systems. Thus, the window id will allow the code to access any required information. Any window in the GUI which is neither a designated class of windows nor is in the list structure will exhibit the normal, default behaviour of the operating system. The invention has the advantage over the prior art in direct manipulation techniques can be used more effectively. The user can drag and drop an icon to a target position in a single operation.

Claims: A method for transferring graphical objects from a source window (100) to a target window (101) of a graphical user interface on a computer display, the method being characterised by the steps of: during a first drag a drop operation in a first mode, determining (173) that a first graphical object has hit an interior boundary of the target window, scrolling (203) the target window so long as the first graphical object continues to hit the interior boundary and locating the first graphical object at the target location at a conclusion of the first drag and drop operation; and during a second drag and drop operation in a second mode, which prevents the scrolling of the target window, dragging a second graphical object from the source window past an interior boundary of the target window. A method as claimed in claim 1 further comprising the step of determining (181) whether the target window is scrollable during a drag and drop operation. A method as claimed in claim 1 or claim 2 further comprising the steps of: storing an initial position of a pointer at commencement of the drag and drop operation to determine that the graphical object originated in the source window; and refreshing a boundary position of the pointer as the graphical object continues to hit the interior boundary. A method as claimed in claim 2 wherein the target window is determined to be scrollable by referring to a class of the target window. The method as claimed in claim 2 wherein the target window is determined to be scrollable by referring to a list of scrollable target windows. A system for transferring a graphical object, in a drag and drop operation, from a source window to a target window of a graphical user interface on a computer display, the system being characterised in that it comprises: means for determining that a graphical object has hit an interior boundary of a target window; means responsive to a determination that the drag and drop operation is in a first mode for scrolling the target window so long as the graphical object continues to hit the interior boundary wherein the graphical object is located at the target location at the conclusion of the drag and drop operation; and means responsive to a determination that the drag and drop operation is in a second mode, which prevents the scrolling of the target window, for dragging the graphical object past the interior boundary of the target window. The system as claimed in claim 6 further comprising means for determining whether the target window is scrollable during a drag and drop operation. A system as claimed in claim 6 further comprising: means for storing an initial position of a pointer at commencement of the drag and drop operation to determine that the graphical object originated in the source window; and means for refreshing a boundary position of the pointer as the graphical object continues to hit the interior boundary. A system as claimed in claim 7 wherein the target window is determined to be scrollable by referring to a class of the target window. A system as claimed in claim 7 wherein the target window is determined to be scrollable by referring to a list of scrollable target windows. A system as claimed in any of claims 6 to 10 which further comprises: a memory coupled to a system bus for storing sets of instructions to operate the system; a processor coupled to the system bus to execute the sets of instructions; and a display coupled to the system bus for displaying the graphical user interface. A computer program product in a computer memory for transferring a graphical object, in a drag and drop operation, from a source window to a target window of a graphical user interface, on a computer display, the computer program product being characterised in that it comprises: computer program code means to make the computer execute procedure to determine that a graphical object has hit an interior boundary of a target window; computer program code means, responsive to a determination that the drag and drop operation is in a first mode, to make the computer execute procedure to scroll the target window so long as the graphical object continues to hit the interior boundary within the graphical object is located at the target location at the conclusion of the drag and drop operation; and computer program code means, responsive to a determination that the drag and drop operation is in a second mode, which prevents the scrolling of the target window, to make the computer execute procedure to drag the graphical object past the interior boundary of the target window.

Inventors: LI SHIH-GONG, SHRADER THEODORE JACK LONDON, LI, SHIH-GONG, SHRADER, THEODORE JACK LONDON
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES
Application year: 1994
Main classification: G06F3
IPC codes: G06F3